O Level Chemistry: Fuel Cells in Energy Changes

Combustion reactions are only one means of extracting useful energy from fuels. Over the years, scientists all over the world have explored the possibility of converting the chemical energy of fuels directly to electricity.

They call this new possibility as “Fuel Cell” – A chemical cell in which reactants (usually a fuel and oxygen) are continuously supplied to produce electricity directly.

The most common type of fuel cell is the Hydrogen-Oxygen Fuel Cell which is used as a source of electrical power in many spaceships and vehicles.

A Hydrogen-Oxygen Fuel Cell is indeed a Chemical Cell and consists of 2 electrodes – a positive electrode (Cathode) and a negative electrode (Anode).

At the Cathode: O2(g) + 2H2O(l) + 4e– –> 4OH–(aq)

At the Anode: 2H2(g) + 4OH–(aq) –> 4H2O(l) + 4e–

Overall reaction: O2(g) + 2H2(g) –> 2H2O(l)

As you can see from the overall reaction, it involves the conversion of hydrogen and oxygen gas to water. This is similar to Combustion of Hydrogen.

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This is basically what my assignment is about. Finding a viable fuel that is ‘good’ and how to synthesis it, is it safe for use and its storing capability. This included everything! But unfortunately I’ll have to keep looking for my fuel. Thanks Sean 😀

Advantage- It’s renewable. Does not pollute the environment as the product is only water.
Disadvantage- Hydrogen is available in a limited amount. Also, this is very expensive as it needs a lot of voltage. (And we can use cryolite to prevent that)

I have a question about the electrodes. Why are they exchanged? Can you please explain why Anode which is usually positive is negative here. And Cathode which is usually negative, positive here?